I think it would depend on the beach you go to...Miami beaches are pretty busy, aren't they? I would be afraid someone might steal my baby!
Also, if dogs are allowed, then you might possibly run into one that was big and not so friendly towards your little one.
There was a post on here recently about someone whose little one got attacked by other large dogs (unleashed and uncontrolled) and the little one was killed.
I'm sure there are other opinions....I am only speaking for me and my little Sassy. I just couldn't take the chance.